Open source has EVERYTHING to do with security, but not in the sense savers means.

Theoretically if you are root then you should be able to create a new admin right?

Not just theoretically...
As root in OS X, you can do everything, just like in Linux/UNIX. This includes creating a new user with admin rights, celeting an existing user, even without having his/her password AND messing up the system, which I managed to do while playing around too much...

So be careful with what you do, but as long as you're just creating/erasing users, the system won't take any harm...
I played around with system files, resulting in Kernel Panics and happy reinstallation parties